1. Field of the Invention
The present invention relates to a display device, and more particularly, to a display device that is designed to prevent defects caused by static electricity generated during the fabrication process of a display device or by a current applied during inspection.
2. Description of the Background Art
Various electrical equipment provides various information to a user by using flat panel display devices such as a liquid crystal display device, a plasma display panel device, a field emission device, an electrophoretic display device, and an organic light emitting diode display device.
Display devices convert a video signal input from the outside into a data voltage, and displays an image related to the video signal in a plurality of pixels in response to a data voltage. These display devices each include a substrate where thin film transistors (TFT), wiring, and circuitry including pads connected to drive integrated circuits (D-IC) for driving the display device are formed. Such a substrate is referred to as an array substrate or backplane.
Electrical charges may be generated during various steps of a fabrication process of an array substrate for a display device. For example, electrical charges due to frictional electrification may be generated during high-pressure micro jet (HPMJ) cleaning or other various steps of the array substrate fabrication process. Also, static electricity may enter the substrate through various paths during dry etching or other various steps.
The static electricity entering during the process and the electrical charges resulting from the process may be trapped on organic or inorganic layers on the display substrate. As a result, this affects the electrical properties of transistors formed on the array substrate, causing display defects in the display device. Especially in the case of a display device whose active area is divided into a plurality of driving blocks that are driven by a signal from an individual drive integrated chip (D-IC) or a combination of drive integrated chips, various display defects such as horizontal lines may occur because the electrical charges trapped on organic or inorganic layers on the substrate may differ for each driving block.
To avoid such defects, various additional processes may be performed. For example, in the case of a display device including transistors that use a silicon semiconductor as an active material, additional process like hole doping or plastic processing may be performed to improve the device characteristics.
However, in the case of array substrates using oxide semiconductor transistors, which are getting attention in the recent displays, the use of additional processes for stabilizing the device characteristics may be restricted. For example, doping an oxide semiconductor for improvement of the device characteristics may cause a negative shift in threshold voltage. Moreover, the device characteristics stabilization process may cause an oxygen vacancy in the oxide semiconductor because it requires a high temperature.
Therefore, a display device including a plurality of driving blocks, with drive integrated chips (D-IC) bonded directly to a substrate, may suffer from defects due to luminance differences between the driving blocks caused by electrical charges generated or entering during the fabrication process of the display device.
Moreover, a charge difference is generated between gate lines and data lines because the gate lines and the data lines are separated from each other, and this increases the possibility of leaving floating impurities or organic impurities on top of the gate lines or on overlapping portions between the gate lines and the data lines or overlapping portions between the gate lines and source/drain electrodes.